A coalition of liberal advocacy groups is mobilizing its members to whip Democratic senators against voting for any deficit-reduction deal that cuts safety-net benefits.

The groups divide the caucus up into three categories -- the "weak-kneed," who they fear may agree to benefit cuts; the "wavering," who have signaled discomfort with the idea but haven't committed; and the "champions" whose support they're confident of. Via petition, they are urging their supporters to call their senators and ask for and record their positions on benefit cuts, with the dual goals of pressuring Democrats to oppose reducing Medicare, Medicaid and Social Security benefits and of providing their supporters continually updated information on where key members stand on the issue.

"Senators owe their constituents clarity about whether they'll stand up against any benefit cuts to Medicare, Medicaid, and Social Security," said Victoria Kaplan at MoveOn.org Political Action, in a statement to TPM. "Our whip count seeks to shine a spotlight on whether Democratic Senators will fight for poor, middle class and working families, or if they will cave to Republican demands to favor millionaires and billionaires instead."

The groups running the effort are MoveOn.org, CREDO, Progressives United, Progressive Change Campaign Committee, Social Security Works, Democracy for America (DFA), USAction, Campaign for America's Future, Center for Community Change and Rebuild the Dream. They've categorized senators on the basis of calls from their members to Senate offices and the responses they received.

The campaign is reminiscent of efforts early in the Obama administration to provide outside pressure on Democrats to support progressive priorities. Those efforts were largely abandoned after the White House vigorously objected.

The push comes as Republicans are pressing Democrats to agree to cut entitlement spending by adopting policies such as gradually raising the Medicare eligibility age to 67, slowing the rate at which Social Security benefits grow, and other benefit cuts.